The Houston HIITBAC for African Americans: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Houston HIITBAC for African Americans (NCT02253433), a randomized na study. The primary outcome is Change in Asthma Control Test (ACT) Score.

2. Clinical Question

This is a question about the added contribution of the home-based program when both groups receive enhanced clinic care. It is not a comparison of the home program with no care or with an unspecified usual-care condition. The registry record describes the study as randomized and parallel, but does not report the method used to generate or conceal the allocation sequence.

The primary outcome is assessed at baseline and exit, with exit described as approximately 12 months after enrollment. The registry identifies the ACT as a self-report measure. A result comparing score change could help describe whether the groups followed different trajectories during the study, but the numerical estimates and their uncertainty are not reported in the registry record. Without those estimates, the clinical question can be identified, but its observed answer cannot be characterized from this record.

3. Trial Design

The Houston HIITBAC for African Americans is listed as a randomized, single-masked, parallel-group study of an intervention for asthma. Its status is completed, and the registry lists enrollment as 264. The sponsor is Baylor College of Medicine. The study start is listed as 2015-01-08 and primary completion as 2018-01-26. The phase is listed as NA.

Both groups received enhanced clinic care. The clinic-care description includes a standard appointment, information from a detailed exposure history, asthma education, assessment for allergies, and a customized asthma self-management plan developed using motivational interviewing. The comparator group received this enhanced in-clinic care only.

The other group received the same enhanced in-clinic care plus a customized home-based environmental exposure assessment and a multicomponent exposure reduction and asthma control intervention. The registry describes five home visits over approximately 12 months. The comparison therefore concerns the added home intervention in the context of enhanced clinic care.

The registry identifies the design as parallel and randomized, and masking as single. The identity of the masked party, the randomization procedure, allocation concealment, and the operational details of masking are not reported in the registry record. The planned sample-size justification and the statistical analysis plan are also not reported in the registry record.

The primary outcome is change in ACT score between baseline and exit, with exit described as approximately 12 months after enrollment. A secondary outcome is change in emergency department visits for asthma. The record identifies three outcome measures and three analyses, but does not provide a single reduced primary comparison in the information summarized for this analysis. Numerical group estimates, an effect estimate for the primary comparison, and its uncertainty are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: At baseline, one individual in each group chose not to answer all five ACT questions; therefore a total ACT score could not be calculated for those two individuals (missing data are addressed in the analyses). At exit, among those who completed the study, one person in the enhanced in-clinic group chose not to answer all five ACT questions.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Change in Asthma Control Test (ACT) Score, measured over At baseline (enrollment) and exit (approximately 12 mo after enrollment).

The primary endpoint is change in Asthma Control Test score. The ACT is a validated, self-reported five-question scale assessing asthma control over the previous four weeks. Each question has five possible responses, from 1 (worst) to 5 (best), and the total score ranges from 5 (worst control) to 25 (best control). In general, a total score of 19 or less suggests poor control.

The registry describes measurement at baseline, at enrollment, and at exit, approximately 12 months after enrollment. A change score represents how the ACT score differs between those assessment times. In a randomized comparison, the key group-level question is whether the pattern of change differs between enhanced clinic care alone and enhanced clinic care plus the home intervention. The numerical changes and the between-group estimate are not reported in the registry record.

The ACT is useful as a patient-reported measure because it asks about recent asthma control using a consistent set of questions. Its score is not a direct count of emergency visits or a measure of environmental exposure. It captures the respondent’s reported experience over the stated period. As with any self-reported endpoint, missing answers can prevent calculation of a total score. The registry notes that, at baseline, one individual in each group did not answer all five questions, so a total ACT score could not be calculated for those individuals; the record says missing data are addressed in the analyses.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean change describe?

The primary outcome is continuous: it is a score that can take values across a range rather than a count of events. A mean change summarizes the average difference between the baseline and exit measurements within a group. The comparison of interest is the difference in those average changes between the randomized groups. This is a general explanation of the statistical meaning of the endpoint; the registry record does not report the numerical group changes or a numerical between-group estimate.

A mean is compact and interpretable, but it can conceal variation among individuals. The standard deviation describes the spread of observed values around the mean. It is not the same as the uncertainty in the estimated mean, and it is not a range containing every participant’s score. The record identifies standard deviation as the dispersion measure for the primary outcome, but the numerical standard deviations are not reported in the registry record information used for this analysis.

What does a confidence interval add?

General statistical explanation: a confidence interval expresses the precision of an estimate by giving a range of values compatible with the data and the interval’s statistical procedure. A narrow interval indicates greater precision than a wide interval, all else being equal. The interval does not list the outcomes of individual participants, and it does not by itself establish whether a difference matters to patients. The registry record does not report a confidence interval for the primary comparison.

A hypothesis test and a confidence interval answer related but different questions. A p-value describes how inconsistent the observed data are with a specified null hypothesis under the assumptions of the test. It does not measure the probability that the null hypothesis is true, nor does it quantify the size of a difference. The test used and the primary comparison’s p-value are not reported in the registry record.

What can randomization support?

General statistical explanation: random allocation is intended to make treatment groups comparable, on average, at the start of a study. It can support a causal interpretation of a well-conducted comparison, but it does not guarantee identical baseline characteristics in a particular trial. Interpretation also depends on follow-up, outcome measurement, adherence, missing-data handling, and the analysis population. The record identifies the study as randomized, but the randomization procedure and detailed analysis plan are not reported in the registry record.

The parallel design means the registry describes two groups followed under their assigned interventions rather than a sequence in which all participants receive each condition. The record also identifies masking as single but does not state who was masked. The practical implications of masking for treatment delivery or outcome assessment therefore cannot be determined from the registry record.

How should the planning calculations be read?

The record describes sample-size illustrations using a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. These illustrations consider detecting a stated fraction of the observed effect. They are planning calculations, not observed power. A sample-size calculation can show how a hypothetical effect and chosen assumptions relate to a required sample size; it cannot show that the trial had a particular probability of detecting its actual effect after results are known.

Because the observed effect is not reported in the registry record information used for this analysis, the planning illustrations cannot be independently interpreted as a statement about the size of the observed ACT difference. The trial’s own design justification and any sample-size assumptions used when planning the study are not reported in the registry record. These are distinct from retrospective planning illustrations.

Why does a continuous outcome need careful comparison?

General statistical explanation: comparing changes can account for the fact that participants have baseline scores as well as exit scores. The exact analysis may compare change scores, adjust for baseline values, or use another model; different approaches make different assumptions and can yield estimates with different precision. The analysis method for the ACT outcome is not reported in the registry record, so it should not be inferred from the fact that the endpoint is a change in mean score.

Missing observations also matter. A participant without a complete set of ACT answers may not have a calculable total score at a given assessment. The registry reports that one individual in each group had incomplete ACT answers at baseline and says missing data are addressed in the analyses. The specific missing-data method, the assumptions it makes, and the analysis population are not reported in the registry record. Those details are necessary for evaluating whether the results could be sensitive to missing outcomes.

For event outcomes such as emergency department visits, analysis choices depend on the form and distribution of the recorded data. The statistical method for that secondary outcome is not reported in the registry record. General methods explanations should not be mistaken for descriptions of methods actually used in this study; the registry information does not establish whether a particular model, adjustment, or sensitivity analysis was performed.

10. Multiplicity, Missing Data and Analysis Populations

The record identifies three outcome measures and three analyses. The primary outcome is change in ACT score, and change in emergency department visits for asthma is listed as a secondary outcome. The registry information used for this analysis indicates that the primary outcome has several categories or time points and is not reduced to one comparison. A single primary estimate is therefore not available for a focused numerical interpretation.

When studies examine more than one outcome, time point, or comparison, the chance of at least one apparently notable result can increase if each is assessed separately. General statistical explanation: multiplicity procedures can address that issue by defining a primary comparison in advance or adjusting the interpretation of multiple tests. Whether any such procedure was planned or used is not reported in the registry record. The outcome hierarchy, any prespecified primary contrast, and any adjustment for multiple testing are not reported in the registry record.

Missingness is relevant to the ACT endpoint. At baseline, one individual in each group did not answer all five questions, so a total score could not be calculated for those individuals. The registry says missing data are addressed in the analyses, but the method is not reported in the registry record. The number of participants with missing exit outcomes, the reasons for missingness, and the assumptions or sensitivity analyses used to address missing data are not reported in the registry record.

The analysis populations are not reported in the registry record. It is therefore not possible to determine from this information whether the reported analyses, if available, would include everyone as randomized, only participants with observed outcomes, or another defined group. The record’s description of participants who completed the study does not, by itself, specify the full analysis population or establish how missing outcomes were handled.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry lists serious adverse events separately for the two groups. For Enhanced Clinic Care, zero participants are listed as affected among 130 at risk. For Enhanced Clinic Care + Home Intervention, zero participants are listed as affected among 134 at risk. The entries for other adverse events also list zero affected participants in each group, with the same group-specific numbers at risk.

The record separately lists one death in the Enhanced Clinic Care group and one death in the Enhanced Clinic Care + Home Intervention group. The death counts should not be combined with, or treated as a description of, the serious adverse event counts. The registry information does not report the circumstances, timing, cause, or relationship of either death to the intervention.

These entries are counts recorded in the registry, not proof that an intervention caused or prevented an event. Zero reported affected participants does not establish that no event of any kind occurred; it describes the entries in these registry categories. The duration and completeness of safety surveillance, definitions used, and attribution assessments are not reported in the registry record. The figures should therefore be read as registry safety counts with limited contextual detail, not as a causal comparison of risk.

12. What the Result Does, and Does Not, Mean

The registry record describes a randomized study comparing enhanced clinic care alone with the same clinic care plus a home-based environmental exposure and asthma-control intervention. It identifies change in ACT score as the primary endpoint and describes measurement at baseline and exit, approximately 12 months after enrollment. These details establish what the study set out to compare.

The record information used for this analysis does not include a single numerical comparison of ACT change between groups. The direction and magnitude of the observed difference, its precision, and its statistical evidence are therefore not reported in the registry record. It is not possible to conclude from the outcome information available whether the groups changed differently, whether any difference was large or small, or how uncertain an estimate would be.

That limitation is not a finding of no effect. An unreported estimate cannot be interpreted as zero, and an unavailable p-value cannot be interpreted as evidence for or against a difference. The primary outcome’s multiple categories or time points are not reduced to one comparison in the registry record information used.

The ACT reflects self-reported asthma control over the previous four weeks. It is not itself a direct measure of emergency department use, a complete account of asthma experience, or a measure of environmental exposure. The secondary outcome of change in emergency department visits is listed, but its numerical results are not reported in the registry record.

The safety entries describe registry counts, including one death in each group, without reporting circumstances or attribution. They do not establish that the intervention caused or prevented a death or other event. The record can describe the design, intervention contrast, endpoints, and recorded safety counts, but the available numerical outcome information does not support a conclusion about the observed primary treatment effect.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of an add-on comparison: both groups received enhanced clinic care, while one group also received the home-based intervention. That structure makes the intended contrast the additional home component in the setting of the clinic program, rather than home intervention versus no intervention. Clear definition of the comparator is essential when interpreting an estimated treatment effect.

The primary outcome is a patient-reported continuous score measured at baseline and exit. This raises familiar analytical questions about how change is defined, how baseline measurements are incorporated, how variation is summarized, and how incomplete questionnaires are handled. The registry notes incomplete baseline ACT responses and says missing data are addressed in the analyses, but the specific analytical approach is not reported in the registry record.

The study also illustrates why a registry’s outcome labels are not a substitute for a complete results presentation. A primary outcome can be identified without a single interpretable group comparison being available. Without an estimate and a measure of precision, readers cannot assess the observed magnitude or uncertainty, regardless of the design label or the nominal study enrollment.

Finally, the registry separates adverse event counts from deaths, which should be interpreted as distinct entries unless the record supplies a basis for linking them. The available safety details do not describe event circumstances or attribution. Careful statistical interpretation depends not only on counts, but also on definitions, follow-up, analysis populations, and the uncertainty around comparisons. Several of those details are not reported in the registry record.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The main limitation for interpreting the primary result is that a single numerical comparison of ACT change is not reported in the registry record information used for this analysis. Group-level changes, a between-group estimate, and its precision are not available for interpretation. The outcome summary indicates that several categories or time points are not reduced to one comparison.

The registry describes the study as randomized and single-masked, but does not report the randomization procedure, the identity of the masked party, or the operational details of masking. The statistical analysis plan, including the exact ACT model or contrast, is not reported in the registry record. The analysis populations and the handling of missing data beyond the general statement that missing data are addressed in the analyses are also not reported.

At baseline, one individual in each group did not answer all five ACT questions, preventing calculation of a total score for those individuals. The registry information does not give the full pattern of missing outcome data across follow-up or the reasons for missingness. It also does not report sensitivity analyses that would show how results might change under alternative assumptions.

The intervention description specifies five home visits over approximately 12 months, but adherence, variation in intervention delivery, and the amount of exposure-reduction activity completed are not reported in the registry record. The registry lists an emergency department outcome without its numerical results or analysis details. Safety entries list event counts but do not provide circumstances, timing, or attribution for deaths. These omissions limit interpretation of both effectiveness and safety from the registry information alone.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: The Houston HIITBAC for African Americans — NCT02253433.
• Registry record last updated 2018-11-14; status last verified 2018-11.
• Results first posted 2018-11-14.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

The registry record identifies NCT02253433 as a completed randomized, single-masked, parallel-group study sponsored by Baylor College of Medicine. It lists enrollment as 264 and concerns asthma among African-American adults with poorly controlled asthma.

The comparison is enhanced clinic care alone versus enhanced clinic care plus a customized home-based environmental exposure assessment and multicomponent intervention. The home intervention is described as five visits over approximately 12 months. The primary outcome is change in ACT score from baseline to exit, approximately 12 months after enrollment; change in emergency department visits for asthma is listed as a secondary outcome.

The record lists zero serious adverse event participants in each group and one death in each group. A single numerical primary outcome comparison, its precision, detailed analysis methods, and the circumstances or attribution of the deaths are not reported in the registry record.